Many conventional, state of the art robotic force feedback systems rely on at least one force sensor mounted on a robot end effector unit using a type of positioning device, such as a motor and encoder unit, and using a device for applying force a robotic input device having at least one degree of freedom e to an interface device. An example of such a conventional robotic system is illustrated in FIGS. 1 and 2, in which a robot end effector unit, designated by the reference numeral 1, includes a pair of motors 3 and encoders 4, mounted to a gripper-style robot end effector 1. Both distal ends of the gripper “claws” include a force sensor 2. A corresponding interface device, generally designated by the reference numeral 6, includes a pair of handles 9, which pivot at two hinge axes. A motor 7 and encoder 8 is located at each hinge axis. Some type of electronic control system (not shown) is typically included in this conventional robotic system.
Position of the gripper “claws” is controlled through complicated control algorithms utilizing position sensors on both the robot end effector 1 and the interface device 6. These position sensors comprise the encoders 4 on one unit, and the encoders 8 on the other unit. In situations where force sensors are not used, force is generally estimated through the difference between the measured positions of the robot end effector and the interface device, or using an indirect means such as robot end effector motor current. This position control scheme is commonly known as a “force feedback” scheme.
U.S. Pat. No. 6,385,509 discloses an example of the force feedback robot manipulator control scheme discussed above.